If you want adblocking youtube on iOS I recommend using Safari with the vinegar (paid) extension. (And wipr for general adblocking)
ETA: If I remember correctly, Brave Browser also has ad blocking built in. For youtube as well.
I set up a PiHole in the cloud and set it up so it requires VPN access so that nothing between my phone and the PiHole can fuck with the DNS packets. I VPN into it on my Android and get ad blocking almost* everwhere. I've also configured it to only tunnel DNS lookups, so I don't get charge egress fees for all my phone's traffic, which, granted isn't a lot, but whatever.
* Sadly, it doesn't block YouTube ads, but I rarely access YouTube on my phone anyways.